The present invention relates to an ultrasonic device for determining the existence and/or the position of an object. It is used in metrology and particularly in the position control of various objects, as for example the fuel assembly rods of nuclear reactors during inspections.
In per se known manner as ultrasonic probe comprises an ultrasonic transducer, a supply circuit for said transducer consisting of an electrical pulse generator and a circuit for processing the signal supplied by the transducer in response to the ultrasonic echoes which it receives, said echoes coming from the various obstacles present on the path of the ultrasonic beam.
By means of such a probe it is possible to determine the position of an object, e.g. the axis of a cylinder. For this purpose it is merely necessary to move the probe in a direction perpendicular to said axis and plot the amplitude of the signal supplied by the transducer. This amplitude is firstly zero when the probe does not face the cylinder and then increases when the ultrasonic beam starts to strike the cylinder. It then passes through a maximum when the transducer faces the cylinder axis and then decreases and finally becomes zero again. The passage through the maximum indicates the position of the axis of
A device can be included in a system for regulating the position of the determined object (or in a loop making this position dependent on that of the probe). For this purpose, it is merely necessary to associate therewith means for acting on the position of the object, in order to make the signal supplied by the probe maximum.
Such a position control is a problem occurring e.g. during the inspection of fuel assembly rods of nuclear reactors. These rods must be position controlled with respect to an observation window, throughout the time when they pass in front thereof. The ultrasonic probe is then integral with the window and the rod is displaced in such a way that it is correctly centered relative to the window.
The disadvantage of the aforementioned location device is that it leads to an indefiniteness with regards to the correction direction to be made to the position of the object. Thus, the signals used for controlling the displacement of the object is an error curve, for which the variation of the signal always has the same sign relative to the maximum value. In other words, the function representing the signal is even. Thus, a priori, no information is possible on the direction in which it is necessary to move the object in order to make the detected amplitude maximum.